The asymmetric catalytic schema (REF ) that gives
the Selkov model a negative slope for its fixed points also leads to
vorticity in the stationary trajectories, which has the same sign
for both classical mean-field equations and escape trajectories. Thus
excursions that return to a fixed point are even more exaggerated
loops in the Selkov model than in the cross-catalytic CRN. Escape
trajectories also form caustics, leading to regions in the state space
for which the eikonal approximation becomes invalid, a phenomenon
noted for eikonals in first-passage problems by Maier and
Stein [1]} and remarked in this model
in [2]}.
